zeroshade commented on code in PR #429: URL: https://github.com/apache/arrow-go/pull/429#discussion_r2178042424
########## parquet/example_write_read_pq_test.go: ########## @@ -0,0 +1,183 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you under the Apache License, Version 2.0 (the +// "License"); you may not use this file except in compliance +// with the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, +// software distributed under the License is distributed on an +// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +// KIND, either express or implied. See the License for the +// specific language governing permissions and limitations +// under the License. + +package parquet_test + +import ( + "bytes" + "context" + "fmt" + "log" + + "github.com/apache/arrow-go/v18/arrow" + "github.com/apache/arrow-go/v18/arrow/array" + "github.com/apache/arrow-go/v18/arrow/memory" + "github.com/apache/arrow-go/v18/parquet" + "github.com/apache/arrow-go/v18/parquet/compress" + "github.com/apache/arrow-go/v18/parquet/file" + "github.com/apache/arrow-go/v18/parquet/pqarrow" +) + +// In a real project, this should be tuned based on memory usage and performance needs +const batchSize = 2 + +// List of fields to read +var colNames = []string{"intField", "stringField", "listField"} + +func Example_writeReadParquet() { + // --- Phase 1: Writing parquet file --- + + // Create an in-memory buffer to simulate a file + // For writing real file to disk, use os.Create instead + buffer := &bytes.Buffer{} + + // Create a schema with three fields + fields := []arrow.Field{ + {Name: "intField", Type: arrow.PrimitiveTypes.Int32, Nullable: false}, + {Name: "stringField", Type: arrow.BinaryTypes.String, Nullable: false}, + {Name: "listField", Type: arrow.ListOf(arrow.PrimitiveTypes.Float32), Nullable: false}, + } + + schema := arrow.NewSchema(fields, nil) + + // Create parquet writer props with snappy compression + writerProps := parquet.NewWriterProperties( + parquet.WithCompression(compress.Codecs.Snappy), + ) + + // Create arrow writer props to store the schema in the parquet file + arrowWriterProps := pqarrow.NewArrowWriterProperties( + pqarrow.WithStoreSchema(), + ) Review Comment: Should we elaborate in the comment about the benefit to storing the Arrow schema in the metadata? ########## parquet/example_write_read_pq_test.go: ########## @@ -0,0 +1,183 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you under the Apache License, Version 2.0 (the +// "License"); you may not use this file except in compliance +// with the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, +// software distributed under the License is distributed on an +// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +// KIND, either express or implied. See the License for the +// specific language governing permissions and limitations +// under the License. + +package parquet_test + +import ( + "bytes" + "context" + "fmt" + "log" + + "github.com/apache/arrow-go/v18/arrow" + "github.com/apache/arrow-go/v18/arrow/array" + "github.com/apache/arrow-go/v18/arrow/memory" + "github.com/apache/arrow-go/v18/parquet" + "github.com/apache/arrow-go/v18/parquet/compress" + "github.com/apache/arrow-go/v18/parquet/file" + "github.com/apache/arrow-go/v18/parquet/pqarrow" +) + +// In a real project, this should be tuned based on memory usage and performance needs +const batchSize = 2 + +// List of fields to read +var colNames = []string{"intField", "stringField", "listField"} + +func Example_writeReadParquet() { + // --- Phase 1: Writing parquet file --- + + // Create an in-memory buffer to simulate a file + // For writing real file to disk, use os.Create instead + buffer := &bytes.Buffer{} + + // Create a schema with three fields + fields := []arrow.Field{ + {Name: "intField", Type: arrow.PrimitiveTypes.Int32, Nullable: false}, + {Name: "stringField", Type: arrow.BinaryTypes.String, Nullable: false}, + {Name: "listField", Type: arrow.ListOf(arrow.PrimitiveTypes.Float32), Nullable: false}, + } + + schema := arrow.NewSchema(fields, nil) + + // Create parquet writer props with snappy compression + writerProps := parquet.NewWriterProperties( + parquet.WithCompression(compress.Codecs.Snappy), + ) + + // Create arrow writer props to store the schema in the parquet file + arrowWriterProps := pqarrow.NewArrowWriterProperties( + pqarrow.WithStoreSchema(), + ) + + // Create a parquet writer + writer, err := pqarrow.NewFileWriter(schema, buffer, writerProps, arrowWriterProps) + if err != nil { + log.Fatalf("Failed create parquet writer: %v", err) + } + + // Create a record builder + recordBuilder := array.NewRecordBuilder(memory.DefaultAllocator, schema) + + // Create a builder for each field + intFieldIdx := schema.FieldIndices("intField")[0] + stringFieldIdx := schema.FieldIndices("stringField")[0] + listFieldIdx := schema.FieldIndices("listField")[0] + + intFieldBuilder := recordBuilder.Field(intFieldIdx).(*array.Int32Builder) + stringFieldBuilder := recordBuilder.Field(stringFieldIdx).(*array.StringBuilder) + listFieldBuilder := recordBuilder.Field(listFieldIdx).(*array.ListBuilder) + + // Get the builder for the list's values (Float32) + fl32Builder := listFieldBuilder.ValueBuilder().(*array.Float32Builder) + + // Append values for each field + intFieldBuilder.AppendValues([]int32{38, 13, 53, 93, 66}, nil) + stringFieldBuilder.AppendValues([]string{"val1", "val2", "val3", "val4", "val5"}, nil) + + // Append five lists, each containing the same float32 values + for i := 0; i < 5; i++ { + listFieldBuilder.Append(true) + fl32Builder.AppendValues([]float32{1.0, 2.0, 4.0, 8.0}, nil) + } + + // Create a record + record := recordBuilder.NewRecord() + if err := writer.Write(record); err != nil { + log.Fatalf("Failed to write record: %v", err) + + } + + record.Release() + recordBuilder.Release() + + // IMPORTANT: Close the writer to finalize the file + if err := writer.Close(); err != nil { + log.Printf("Failed to close parquet writer: %v", err) Review Comment: `log.Fatalf`? ########## parquet/example_write_read_pq_test.go: ########## @@ -0,0 +1,183 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you under the Apache License, Version 2.0 (the +// "License"); you may not use this file except in compliance +// with the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, +// software distributed under the License is distributed on an +// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +// KIND, either express or implied. See the License for the +// specific language governing permissions and limitations +// under the License. + +package parquet_test + +import ( + "bytes" + "context" + "fmt" + "log" + + "github.com/apache/arrow-go/v18/arrow" + "github.com/apache/arrow-go/v18/arrow/array" + "github.com/apache/arrow-go/v18/arrow/memory" + "github.com/apache/arrow-go/v18/parquet" + "github.com/apache/arrow-go/v18/parquet/compress" + "github.com/apache/arrow-go/v18/parquet/file" + "github.com/apache/arrow-go/v18/parquet/pqarrow" +) + +// In a real project, this should be tuned based on memory usage and performance needs +const batchSize = 2 + +// List of fields to read +var colNames = []string{"intField", "stringField", "listField"} + +func Example_writeReadParquet() { + // --- Phase 1: Writing parquet file --- + + // Create an in-memory buffer to simulate a file + // For writing real file to disk, use os.Create instead + buffer := &bytes.Buffer{} + + // Create a schema with three fields + fields := []arrow.Field{ + {Name: "intField", Type: arrow.PrimitiveTypes.Int32, Nullable: false}, + {Name: "stringField", Type: arrow.BinaryTypes.String, Nullable: false}, + {Name: "listField", Type: arrow.ListOf(arrow.PrimitiveTypes.Float32), Nullable: false}, + } + + schema := arrow.NewSchema(fields, nil) + + // Create parquet writer props with snappy compression + writerProps := parquet.NewWriterProperties( + parquet.WithCompression(compress.Codecs.Snappy), + ) + + // Create arrow writer props to store the schema in the parquet file + arrowWriterProps := pqarrow.NewArrowWriterProperties( + pqarrow.WithStoreSchema(), + ) + + // Create a parquet writer + writer, err := pqarrow.NewFileWriter(schema, buffer, writerProps, arrowWriterProps) + if err != nil { + log.Fatalf("Failed create parquet writer: %v", err) + } + + // Create a record builder + recordBuilder := array.NewRecordBuilder(memory.DefaultAllocator, schema) + + // Create a builder for each field + intFieldIdx := schema.FieldIndices("intField")[0] + stringFieldIdx := schema.FieldIndices("stringField")[0] + listFieldIdx := schema.FieldIndices("listField")[0] + + intFieldBuilder := recordBuilder.Field(intFieldIdx).(*array.Int32Builder) + stringFieldBuilder := recordBuilder.Field(stringFieldIdx).(*array.StringBuilder) + listFieldBuilder := recordBuilder.Field(listFieldIdx).(*array.ListBuilder) Review Comment: do we need to do the `FieldIndices` calls when we know what the schema is and the indices are since we created the schema? There might be benefits to keeping this as simple as possible ########## parquet/example_write_read_pq_test.go: ########## @@ -0,0 +1,183 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you under the Apache License, Version 2.0 (the +// "License"); you may not use this file except in compliance +// with the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, +// software distributed under the License is distributed on an +// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +// KIND, either express or implied. See the License for the +// specific language governing permissions and limitations +// under the License. + +package parquet_test + +import ( + "bytes" + "context" + "fmt" + "log" + + "github.com/apache/arrow-go/v18/arrow" + "github.com/apache/arrow-go/v18/arrow/array" + "github.com/apache/arrow-go/v18/arrow/memory" + "github.com/apache/arrow-go/v18/parquet" + "github.com/apache/arrow-go/v18/parquet/compress" + "github.com/apache/arrow-go/v18/parquet/file" + "github.com/apache/arrow-go/v18/parquet/pqarrow" +) + +// In a real project, this should be tuned based on memory usage and performance needs +const batchSize = 2 + +// List of fields to read +var colNames = []string{"intField", "stringField", "listField"} + +func Example_writeReadParquet() { + // --- Phase 1: Writing parquet file --- + + // Create an in-memory buffer to simulate a file + // For writing real file to disk, use os.Create instead + buffer := &bytes.Buffer{} + + // Create a schema with three fields + fields := []arrow.Field{ + {Name: "intField", Type: arrow.PrimitiveTypes.Int32, Nullable: false}, + {Name: "stringField", Type: arrow.BinaryTypes.String, Nullable: false}, + {Name: "listField", Type: arrow.ListOf(arrow.PrimitiveTypes.Float32), Nullable: false}, + } + + schema := arrow.NewSchema(fields, nil) + + // Create parquet writer props with snappy compression + writerProps := parquet.NewWriterProperties( + parquet.WithCompression(compress.Codecs.Snappy), + ) + + // Create arrow writer props to store the schema in the parquet file + arrowWriterProps := pqarrow.NewArrowWriterProperties( + pqarrow.WithStoreSchema(), + ) + + // Create a parquet writer + writer, err := pqarrow.NewFileWriter(schema, buffer, writerProps, arrowWriterProps) + if err != nil { + log.Fatalf("Failed create parquet writer: %v", err) + } + + // Create a record builder + recordBuilder := array.NewRecordBuilder(memory.DefaultAllocator, schema) + + // Create a builder for each field + intFieldIdx := schema.FieldIndices("intField")[0] + stringFieldIdx := schema.FieldIndices("stringField")[0] + listFieldIdx := schema.FieldIndices("listField")[0] + + intFieldBuilder := recordBuilder.Field(intFieldIdx).(*array.Int32Builder) + stringFieldBuilder := recordBuilder.Field(stringFieldIdx).(*array.StringBuilder) + listFieldBuilder := recordBuilder.Field(listFieldIdx).(*array.ListBuilder) + + // Get the builder for the list's values (Float32) + fl32Builder := listFieldBuilder.ValueBuilder().(*array.Float32Builder) + + // Append values for each field + intFieldBuilder.AppendValues([]int32{38, 13, 53, 93, 66}, nil) + stringFieldBuilder.AppendValues([]string{"val1", "val2", "val3", "val4", "val5"}, nil) + + // Append five lists, each containing the same float32 values + for i := 0; i < 5; i++ { + listFieldBuilder.Append(true) + fl32Builder.AppendValues([]float32{1.0, 2.0, 4.0, 8.0}, nil) + } + + // Create a record + record := recordBuilder.NewRecord() + if err := writer.Write(record); err != nil { + log.Fatalf("Failed to write record: %v", err) + + } + + record.Release() + recordBuilder.Release() + + // IMPORTANT: Close the writer to finalize the file + if err := writer.Close(); err != nil { + log.Printf("Failed to close parquet writer: %v", err) + } + + // --- Phase 2: Reading parquet file --- + + // Create a Parquet reader from the in-memory buffer + // For reading real file from disk, use file.OpenParquetFile() instead + fileReader, err := file.NewParquetReader(bytes.NewReader(buffer.Bytes())) + if err != nil { + log.Fatalf("Failed to create parquet reader: %v", err) + } + defer func() { + if err := fileReader.Close(); err != nil { + log.Printf("Failed to close file reader: %v", err) + } + }() + + // Create arrow read props, specifying the batch size + arrowReadProps := pqarrow.ArrowReadProperties{BatchSize: batchSize} + + // Create an arrow reader for the parquet file + arrowReader, err := pqarrow.NewFileReader(fileReader, arrowReadProps, memory.DefaultAllocator) + if err != nil { + log.Fatalf("Failed to create arrow reader: %v", err) + } + + // Get the arrow schema from the file reader + schema, err = arrowReader.Schema() + if err != nil { + log.Fatalf("Failed to get schema: %v", err) + } + + // colIndices can be nil to read all columns. Here, we specify which columns to read + colIndices := make([]int, len(colNames)) + for idx := range colNames { + colIndices[idx] = schema.FieldIndices(colNames[idx])[0] + } + + // Get the current record from the reader Review Comment: ```suggestion // Get a record reader from the file to iterate over ``` ########## parquet/example_write_read_pq_test.go: ########## @@ -0,0 +1,183 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you under the Apache License, Version 2.0 (the +// "License"); you may not use this file except in compliance +// with the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, +// software distributed under the License is distributed on an +// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +// KIND, either express or implied. See the License for the +// specific language governing permissions and limitations +// under the License. + +package parquet_test + +import ( + "bytes" + "context" + "fmt" + "log" + + "github.com/apache/arrow-go/v18/arrow" + "github.com/apache/arrow-go/v18/arrow/array" + "github.com/apache/arrow-go/v18/arrow/memory" + "github.com/apache/arrow-go/v18/parquet" + "github.com/apache/arrow-go/v18/parquet/compress" + "github.com/apache/arrow-go/v18/parquet/file" + "github.com/apache/arrow-go/v18/parquet/pqarrow" +) + +// In a real project, this should be tuned based on memory usage and performance needs +const batchSize = 2 + +// List of fields to read +var colNames = []string{"intField", "stringField", "listField"} + +func Example_writeReadParquet() { + // --- Phase 1: Writing parquet file --- + + // Create an in-memory buffer to simulate a file + // For writing real file to disk, use os.Create instead + buffer := &bytes.Buffer{} + + // Create a schema with three fields + fields := []arrow.Field{ + {Name: "intField", Type: arrow.PrimitiveTypes.Int32, Nullable: false}, + {Name: "stringField", Type: arrow.BinaryTypes.String, Nullable: false}, + {Name: "listField", Type: arrow.ListOf(arrow.PrimitiveTypes.Float32), Nullable: false}, + } + + schema := arrow.NewSchema(fields, nil) + + // Create parquet writer props with snappy compression + writerProps := parquet.NewWriterProperties( + parquet.WithCompression(compress.Codecs.Snappy), + ) + + // Create arrow writer props to store the schema in the parquet file + arrowWriterProps := pqarrow.NewArrowWriterProperties( + pqarrow.WithStoreSchema(), + ) + + // Create a parquet writer + writer, err := pqarrow.NewFileWriter(schema, buffer, writerProps, arrowWriterProps) + if err != nil { + log.Fatalf("Failed create parquet writer: %v", err) + } + + // Create a record builder + recordBuilder := array.NewRecordBuilder(memory.DefaultAllocator, schema) + + // Create a builder for each field + intFieldIdx := schema.FieldIndices("intField")[0] + stringFieldIdx := schema.FieldIndices("stringField")[0] + listFieldIdx := schema.FieldIndices("listField")[0] + + intFieldBuilder := recordBuilder.Field(intFieldIdx).(*array.Int32Builder) + stringFieldBuilder := recordBuilder.Field(stringFieldIdx).(*array.StringBuilder) + listFieldBuilder := recordBuilder.Field(listFieldIdx).(*array.ListBuilder) + + // Get the builder for the list's values (Float32) + fl32Builder := listFieldBuilder.ValueBuilder().(*array.Float32Builder) + + // Append values for each field + intFieldBuilder.AppendValues([]int32{38, 13, 53, 93, 66}, nil) + stringFieldBuilder.AppendValues([]string{"val1", "val2", "val3", "val4", "val5"}, nil) + + // Append five lists, each containing the same float32 values + for i := 0; i < 5; i++ { + listFieldBuilder.Append(true) + fl32Builder.AppendValues([]float32{1.0, 2.0, 4.0, 8.0}, nil) + } + + // Create a record + record := recordBuilder.NewRecord() + if err := writer.Write(record); err != nil { + log.Fatalf("Failed to write record: %v", err) + + } + + record.Release() + recordBuilder.Release() + + // IMPORTANT: Close the writer to finalize the file + if err := writer.Close(); err != nil { + log.Printf("Failed to close parquet writer: %v", err) + } + + // --- Phase 2: Reading parquet file --- + + // Create a Parquet reader from the in-memory buffer + // For reading real file from disk, use file.OpenParquetFile() instead + fileReader, err := file.NewParquetReader(bytes.NewReader(buffer.Bytes())) + if err != nil { + log.Fatalf("Failed to create parquet reader: %v", err) + } + defer func() { + if err := fileReader.Close(); err != nil { + log.Printf("Failed to close file reader: %v", err) + } + }() + + // Create arrow read props, specifying the batch size + arrowReadProps := pqarrow.ArrowReadProperties{BatchSize: batchSize} + + // Create an arrow reader for the parquet file + arrowReader, err := pqarrow.NewFileReader(fileReader, arrowReadProps, memory.DefaultAllocator) + if err != nil { + log.Fatalf("Failed to create arrow reader: %v", err) + } + + // Get the arrow schema from the file reader + schema, err = arrowReader.Schema() + if err != nil { + log.Fatalf("Failed to get schema: %v", err) + } + + // colIndices can be nil to read all columns. Here, we specify which columns to read + colIndices := make([]int, len(colNames)) + for idx := range colNames { + colIndices[idx] = schema.FieldIndices(colNames[idx])[0] + } + + // Get the current record from the reader + recordReader, err := arrowReader.GetRecordReader(context.TODO(), colIndices, nil) + if err != nil { + log.Fatalf("Failed to get record reader: %v", err) + } + defer recordReader.Release() + + for recordReader.Next() { + // Create a record + record := recordReader.Record() + record.Retain() Review Comment: We only need to call `retain` if we need to utilize the record beyond and outside of this loop. Since we only interact with the record in the loop and aren't storing it for use beyond the loop we don't need to call `Retain` and `Release`. Might be better to simplify this ########## parquet/example_write_read_pq_test.go: ########## @@ -0,0 +1,183 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you under the Apache License, Version 2.0 (the +// "License"); you may not use this file except in compliance +// with the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, +// software distributed under the License is distributed on an +// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +// KIND, either express or implied. See the License for the +// specific language governing permissions and limitations +// under the License. + +package parquet_test + +import ( + "bytes" + "context" + "fmt" + "log" + + "github.com/apache/arrow-go/v18/arrow" + "github.com/apache/arrow-go/v18/arrow/array" + "github.com/apache/arrow-go/v18/arrow/memory" + "github.com/apache/arrow-go/v18/parquet" + "github.com/apache/arrow-go/v18/parquet/compress" + "github.com/apache/arrow-go/v18/parquet/file" + "github.com/apache/arrow-go/v18/parquet/pqarrow" +) + +// In a real project, this should be tuned based on memory usage and performance needs +const batchSize = 2 + +// List of fields to read +var colNames = []string{"intField", "stringField", "listField"} + +func Example_writeReadParquet() { + // --- Phase 1: Writing parquet file --- + + // Create an in-memory buffer to simulate a file + // For writing real file to disk, use os.Create instead + buffer := &bytes.Buffer{} + + // Create a schema with three fields + fields := []arrow.Field{ + {Name: "intField", Type: arrow.PrimitiveTypes.Int32, Nullable: false}, + {Name: "stringField", Type: arrow.BinaryTypes.String, Nullable: false}, + {Name: "listField", Type: arrow.ListOf(arrow.PrimitiveTypes.Float32), Nullable: false}, + } + + schema := arrow.NewSchema(fields, nil) + + // Create parquet writer props with snappy compression + writerProps := parquet.NewWriterProperties( + parquet.WithCompression(compress.Codecs.Snappy), + ) + + // Create arrow writer props to store the schema in the parquet file + arrowWriterProps := pqarrow.NewArrowWriterProperties( + pqarrow.WithStoreSchema(), + ) + + // Create a parquet writer + writer, err := pqarrow.NewFileWriter(schema, buffer, writerProps, arrowWriterProps) + if err != nil { + log.Fatalf("Failed create parquet writer: %v", err) + } + + // Create a record builder + recordBuilder := array.NewRecordBuilder(memory.DefaultAllocator, schema) + + // Create a builder for each field + intFieldIdx := schema.FieldIndices("intField")[0] + stringFieldIdx := schema.FieldIndices("stringField")[0] + listFieldIdx := schema.FieldIndices("listField")[0] + + intFieldBuilder := recordBuilder.Field(intFieldIdx).(*array.Int32Builder) + stringFieldBuilder := recordBuilder.Field(stringFieldIdx).(*array.StringBuilder) + listFieldBuilder := recordBuilder.Field(listFieldIdx).(*array.ListBuilder) + + // Get the builder for the list's values (Float32) + fl32Builder := listFieldBuilder.ValueBuilder().(*array.Float32Builder) + + // Append values for each field + intFieldBuilder.AppendValues([]int32{38, 13, 53, 93, 66}, nil) + stringFieldBuilder.AppendValues([]string{"val1", "val2", "val3", "val4", "val5"}, nil) + + // Append five lists, each containing the same float32 values + for i := 0; i < 5; i++ { + listFieldBuilder.Append(true) + fl32Builder.AppendValues([]float32{1.0, 2.0, 4.0, 8.0}, nil) + } + + // Create a record + record := recordBuilder.NewRecord() + if err := writer.Write(record); err != nil { + log.Fatalf("Failed to write record: %v", err) + + } + + record.Release() + recordBuilder.Release() + + // IMPORTANT: Close the writer to finalize the file + if err := writer.Close(); err != nil { + log.Printf("Failed to close parquet writer: %v", err) + } + + // --- Phase 2: Reading parquet file --- + + // Create a Parquet reader from the in-memory buffer + // For reading real file from disk, use file.OpenParquetFile() instead + fileReader, err := file.NewParquetReader(bytes.NewReader(buffer.Bytes())) + if err != nil { + log.Fatalf("Failed to create parquet reader: %v", err) + } + defer func() { + if err := fileReader.Close(); err != nil { + log.Printf("Failed to close file reader: %v", err) + } + }() + + // Create arrow read props, specifying the batch size + arrowReadProps := pqarrow.ArrowReadProperties{BatchSize: batchSize} + + // Create an arrow reader for the parquet file + arrowReader, err := pqarrow.NewFileReader(fileReader, arrowReadProps, memory.DefaultAllocator) + if err != nil { + log.Fatalf("Failed to create arrow reader: %v", err) + } + + // Get the arrow schema from the file reader + schema, err = arrowReader.Schema() + if err != nil { + log.Fatalf("Failed to get schema: %v", err) + } + + // colIndices can be nil to read all columns. Here, we specify which columns to read + colIndices := make([]int, len(colNames)) + for idx := range colNames { + colIndices[idx] = schema.FieldIndices(colNames[idx])[0] + } + + // Get the current record from the reader + recordReader, err := arrowReader.GetRecordReader(context.TODO(), colIndices, nil) + if err != nil { + log.Fatalf("Failed to get record reader: %v", err) + } + defer recordReader.Release() + + for recordReader.Next() { + // Create a record + record := recordReader.Record() + record.Retain() + + // Get columns + intCol := record.Column(colIndices[0]).(*array.Int32) + stringCol := record.Column(colIndices[1]).(*array.String) + listCol := record.Column(colIndices[2]).(*array.List) + listValueCol := listCol.ListValues().(*array.Float32) + + // Iterate over the rows within the current record + for idx := range int(record.NumRows()) { + // For the list column, get the start and end offsets for the current row + start, end := listCol.ValueOffsets(idx) + + fmt.Printf("%d %s %v\n", intCol.Value(idx), stringCol.Value(idx), listValueCol.Float32Values()[start:end]) + } Review Comment: Do we need to grab each column separately like this instead of just calling `fmt.Println(record)` ? -- This is an automated message from the Apache Git Service. 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